An strengthening El Niño could lead California's coast to the highest sea levels ever recorded this year, increasing the risk of widespread and damaging floods during fall and winter. According to the Los Angeles Times, forecasts point to a very strong episode that could also intensify wave action, raise ocean temperatures, and favor a wetter winter, especially in the southern part of the state. One of the indicators already concerning scientists is that, according to a NASA satellite image presented by Mark Merrifield, the sea level in the eastern Pacific was already more than half a foot above the reference level. For fall and winter, he said, it should be well above the average seasonal cycle. Coastal risk in Southern California Merrifield, director of the Climate Impacts and Adaptation Center at the Scripps Institution of Oceanography at the University of California in San Diego, stated during a recent virtual forum that they expect "probably the highest sea levels ever recorded on the California coast associated with this event." He also warned that beaches across the state tend to move inland about 30 meters during El Niño events. This retreat reduces the coastal protection strip. When high waves, high tides, anomalous sea levels, and heavy rains coincide, the probability of flooding increases...
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Forecasts about California anticipate that El Niño could intensify the wave activity, raise ocean temperatures, and promote a wetter winter, especially in the southern part of the state (REUTERS/David Swanson). A strengthening El Niño could bring California's coast to the highest sea levels ever recorded this year, increasing the risk of widespread and damaging floods during fall and winter. According to the Los Angeles Times, forecasts point to a very strong episode that could also intensify wave activity, raise ocean temperatures, and favor a wetter winter, especially in the south of the state. One of the indicators already concerning scientists is that, according to a NASA satellite image presented by Mark Merrifield, the sea level in the eastern Pacific was already more than half a foot above the reference level. For fall and winter, he said, it should be well above the average seasonal cycle. Merrifield, director of the Climate Impacts and Adaptation Center at the Scripps Institution of Oceanography at the University of California in San Diego, stated during a recent virtual forum that they expect "probably the highest sea levels ever recorded on the California coast associated with this event." A strengthening El Niño could bring California's coast to the highest sea levels ever recorded during fall and winter (REUTERS/Mike Blake). He also warned that beaches across the state tend to move inland about 30 meters during El Niño events. This retreat reduces the coastal protection strip. When high waves, high tides, anomalous sea levels, and heavy rains coincide, the probability of coastal flooding, erosion, cliff undermining, and saltwater intrusion into aquifers increases. Merrifield maintained that flooding along the southern California coast will likely be a significant problem during the winter season. He explained that, due to the alteration of storm paths during El Niño, the entire California coast usually experiences higher waves. This pattern has already shown recent signs. In the 2023-24 season, significant flooding was recorded in parts of Ventura, Los Angeles, and San Diego counties, and in one of the most remembered episodes, a wave impacted a containment wall in Ventura, leaving eight injured. NASA detected that the sea level in the eastern Pacific was already more than half a foot above the reference value, according to Mark Merrifield (REUTERS/Mike Blake). The rise associated with El Niño would add to a background trend linked to climate change caused by human activity. In the San Francisco Bay area, where sea levels have risen over the last century, notable peaks were observed during the El Niño seasons of 1982-83, 1997-98, and 2023-24, Merrifield said. At La Jolla Pier, data shared by the scientist show that the average sea level was above normal during the last two considered "very strong" El Niño events: 1997-98 and 2015-16. This year, he added, the episode could reach a similar strength in a matter of months. The expected impact will not be limited to the open coast. Merrifield said that sea level rise can be felt from the San Francisco Bay to San Diego and also affect the Sacramento-San Joaquin delta. In San Francisco, such events have historically caused anomalies of between half a foot and a foot, with peaks usually appearing in November and December. Merrifield warned that California beaches tend to retreat about 30 meters during El Niño events, reducing coastal protection against floods and erosion (REUTERS/Carlos Barria). El Niño is a climate pattern characterized by warmer-than-usual waters in the central and eastern tropical Pacific, along with atmospheric changes that weaken or even reverse the usual east-to-west trade winds. This alteration can direct a persistent band of tropical moisture toward southern California and increase the likelihood of significant rains. Daniel Swain, a climate scientist at the University of California, said during the same forum that ocean temperatures in the eastern tropical Pacific are unprecedented in the critical El Niño region. He stated that, for this time of year, that area is warmer than in any previous recorded year and already surpasses the episodes of 1982-83 and 1997-98. The World Meteorological Organization reported on July 31 that "a strong El Niño is developing" and that it would continue to strengthen until early autumn. Southern California appears to be the most exposed area in winter, after floods recorded in Ventura, Los Angeles, and San Diego during the 2023-24 season (REUTERS/Mike Blake). In a statement, United Nations Secretary-General António Guterres said: "El Niño is not only at our door: it is inside the house and turning up the heat. And this is just an act of warming." Experts emphasized that a very strong El Niño does not guarantee above-average rains in southern California by itself. The 2015-16 episode's precedent shows this uncertainty: despite the episode's intensity, it did not produce above-normal precipitation in that region. Still, Swain told the newspaper that the magnitude of this event significantly increases the chances of a particularly wet winter, especially in the south and possibly also in northern California. He specified that the increased risk is less concentrated in the first third of the rainy season and more in its main phase, between late December and January, February, and March. The sea level rise associated with El Niño adds to climate change and can be felt from the San Francisco Bay to San Diego and the Sacramento-San Joaquin delta (REUTERS/Mike Blake). El Niño could also prolong the marine heatwave off parts of the coast, although that anomaly is not yet fully driven by the climate pattern. Merrifield said that the arrival of even warmer waters opens the possibility of a long-lasting episode, with marked effects on the marine ecosystem and various parts of the food chain. Warming reduces upwelling, the process by which colder, deeper, nutrient-rich waters rise to the surface. This alteration raises concerns about its potential impact on commercial fishing off California and on sensitive marine species to prolonged temperature changes. Among the effects that the California Department of Fish and Wildlife will monitor are levels of domoic acid. Daniel Swain stated that the eastern tropical Pacific records unprecedented ocean temperatures in the key El Niño zone, above those of 1982-83 and 1997-98 (REUTERS/Daniel Cole). In late 2015, this neurotoxin forced the postponement of the Dungeness crab fishing season opening. McGuire indicated that the state, along with the California crab fleet, will begin detection tests in about 60 days as the season approaches. He added that authorities expect domoic acid blooms above average due to increased ocean temperatures. The toxin can be produced by algae of the Pseudo-nitzschia genus and accumulate in shellfish. At low concentrations, it can cause nausea, diarrhea, and illness in humans; at high concentrations, authorities said it can cause short-term memory loss, seizures, and in rare cases, death. The problem also affects wildlife. In recent years, numerous pelicans and sea lions have been poisoned, and additional warming of the sea could add pressure on California's kelp forests. Nate Jaros, vice president of animal care for fish and invertebrates at the Aquarium of the Pacific, said that previous marine heatwaves have caused a 90% decline in northern California's bull kelp habitats since 2014. That loss impacts other species, including the white abalone, which is endangered. Even without fully accounting for El Niño's effect, ocean temperatures have already spiked along some stretches of the coast. Swain said that in parts of southern California, recent fog was not accompanied by cool, moist air, but by a mass of warm, humid, and stifling air, and he added that warming is also beginning to be observed off the northern coast of the state.